1. Field of the Invention
The present invention is directed to a method and system for controlling scope of user participation in an ongoing communication session. The techniques described here can extend to use with respect to various types of communication sessions, whether circuit-switched or packet-switched.
2. Description of Related Art
As a general matter, it is known to establish a conference session over a telecommunications network between multiple user stations, each operated by a respective user. An multipoint control unit (MCU) can reside in the telecommunications network and can function as a bridging or switching device between the participating stations, to support the conference session.
A participating station can initiate the conference session by sending a session setup message to the MCU, identifying the other desired participant(s). The MCU may then seek to connect with the designated other participants, such as by forwarding the session setup message to each other party. Upon successful setup of the session, the MCU may then establish a communication session respectively with each participating station, and the MCU may bridge together the communication sessions, so that the users at the stations can confer with each other via the MCU.
By way of example, consider two users, A and B, operating respective user stations. A wishes to engage in a conference session with B and therefore instructs his user station to initiate the conference. A's user station may then responsively execute a session initiation protocol (SIP) client application to generate and send a SIP INVITE message to the MCU, seeking to invite B to the conference session. The MCU will then treat that INVITE message as a request to establish a conference session with B. To establish the conference session, the MCU may send another INVITE to B's station, seeking to set up a session with B.
Upon receipt of the INVITE from the MCU, B's station may execute a SIP client application to accept the invitation, by sending a SIP 200 OKAY message back to the MCU. Upon receipt of the 200 OKAY, the MCU would then send a 200 OKAY to A's station. In turn, A's station would send a SIP ACKNOWLEDGEMENT to the MCU, and the MCU would send an ACKNOWLEDGEMENT to B's station. As a result, two communication sessions or “legs” will have been initiated, one between A's station and the MCU, and another between the MCU and B's station.
Once these legs have been initiated, the two stations may then begin communicating with the MCU via respective real time protocol (RTP) sessions. Client A's station would communicate with the MCU via one RTP session, and client B's station would communicate with the MCU via another RTP session. The MCU would then bridge together the two sessions, thereby allowing A and B to communicate with each other. A real-time control protocol (RTCP) could be used to manage each session and to tear down the sessions when they are finished.